The navigation data are digitally collected using a Satellite Integrated Navigation (SINS) system. The system is a space-based satellite navigation maintained by the United States government and is accessible using a satellite receiver. This system provides navigational accuracy of approximately 200 m.The Data Acquistion, Processing, and Storage (DAPS) group performs a number of processing steps to the navigation data once it is collected which can vary by cruise. These steps are outlined within the header information in each individual digital navigation (.05x) space-delimited ASCII data file. The header information rows are indicated by lines beginning with the character "!". There is no information on how the single-beam bathymetry, gravity, and magnetic data were collected. For each data gathering cruise leg, the available data in the following categories are forwarded to NGDC: navigation, gravity, magnetics, bathymetry, and seismic shot points. The available data for each cruise leg are re-formatted and combined into the Marine Geophysical Data Exchange Format (MGD77) and into the internal NGDC SEIS-NAV format by USGS using several USGS developed FORTRAN programs.The FORTRAN programs sample the navigation to every integer minute of the cruise. When necessary, the latitudes and longitudes are linearly interpolated. If the time between the actual navigation fixes exceeds five minutes, no data are included in the MGD77 file.To build the MGD77 file, gravity, magnetics, and bathymetry are added to this sampled navigation. When necessary, gravity, magnetics, and bathymetry data are linearly interpolated if the time between the actual data samples does not exceed five minutes. If a time gap exceeds this, the data are not reported.The navigation data are merged with the seismic shot point data in a SEIS- NAV format file. For this file, navigation data are interpolated for each shot point. Both types of files are written to magnetic tape and sent to NGDC.
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| Range of values | |
|---|---|
| Minimum: | 19840616 |
| Maximum: | 19840808 |
| Units: | Year, month, day |
| Range of values | |
|---|---|
| Minimum: | 0 |
| Maximum: | 2359 |
| Units: | hours and decimal minutes |
| Range of values | |
|---|---|
| Minimum: | 38.22030 |
| Maximum: | 43.04180 |
| Units: | decimal degrees |
| Range of values | |
|---|---|
| Minimum: | -129.34190 |
| Maximum: | -123.50920 |
| Units: | decimal degrees |
| Range of values | |
|---|---|
| Minimum: | 1 |
| Maximum: | 3 |
| Units: | 1 = observed fix, 3 = interpolated fix, nil = unspecified |
| Range of values | |
|---|---|
| Minimum: | 0.082 |
| Maximum: | 6.37 |
| Units: | seconds |
| Range of values | |
|---|---|
| Minimum: | 61.5 |
| Maximum: | 4780.5 |
| Units: | decimal meters |
| Range of values | |
|---|---|
| Minimum: | 63 |
| Maximum: | 63 |
| Units: | 01-55 Matthews' Zones with zone , 59 Matthews' Zones, no zone specified, 60 S. Kuwahara Formula, 61 Wilson Formula, 62 Del Grosso Formula, 63 Carter's Tables, 88 Other (see Add. Doc.), 97 Computed using 1500 meters/sec, 98 Unknown if Corrected, 99 Unspecified |
| Range of values | |
|---|---|
| Minimum: | 1 |
| Maximum: | 3 |
| Units: | 1 - Observed, 3 - Interpolated (Header Seq. 12), 9 - Unspecified |
| Range of values | |
|---|---|
| Minimum: | 49820 |
| Maximum: | 53354 |
| Units: | gammas |
| Range of values | |
|---|---|
| Minimum: | --464 |
| Maximum: | 692 |
| Units: | gammas |
Dave Cacchione (Chief Scientist, USGS Western Region); Dave Drake (Chief Scientist, USGS Western Region)
These data and information are intended for science researchers,students, policy makers, and general public. These data are not to be used for navigation purposes. The data are reformatted into MGD77T standard format for inclusion into NOAA's NGDC geophysical database. From there the data will be made available to GeoMapApp ( http://www.geomapapp.org/ ) and Virtual Ocean ( http://www.virtualocean.org/ ) Earth-browsing software. Access to the data is also provided via the USGS Coastal and Marine Geoscience Data System ( http://cmgds.marine.usgs.gov/ ).
Online Links:
Are there legal restrictions on access or use of the data?Access_Constraints: None. These data are held in the public domain.
Use_Constraints:This information is not intended for navigational purposes. Read and fully comprehend the metadata prior to data use. Uses of these data should not violate the spatial resolution of the data. Where these data are used in combination with other data of different resolution, the resolution of the combined output will be limited by the lowest resolution of all the data. Acknowledge the U.S. Geological Survey in products derived from these data. Share data products developed using these data with the U.S. Geological Survey.This database has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.Although this Federal Geographic Data Committee-compliant metadata file is intended to document these data in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology.
Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
| Data format: | tab-delimited ASCII text files. in format MGD77t (version 10) MGD77 Size: 2.4 |
|---|---|
| Network links: |
http://www.ngdc.noaa.gov/mgg/trk/trackline/farnella/f384nc/mgd77/ |